Table 1 Age-adjusted characteristics of Nurses’ Health Study II participants, by IGF-1 levels at time of biopsy
Characteristic | Below median IGF-1 n = 76 | Above median IGF-1 n = 75 | Below median IGFBP-3 n = 75 | Above median IGFBP-3 n = 76 |
|---|---|---|---|---|
Mean (SD) | ||||
 Age (years)a | 44.62 (5.09) | 41.25 (4.59) | 43.92 (5.44) | 41.99 (4.61) |
 Age at menarche (years) | 12.51 (1.43) | 12.79 (1.30) | 12.72 (1.56) | 12.76 (1.42) |
 Body Mass Index (kg/m2) | 26.51 (6.65) | 24.47 (4.00) | 25.22 (5.32) | 25.55 (5.48) |
 Alcohol, g/day | 2.67 (4.32) | 2.92 (5.06) | 3.28 (5.84) | 2.42 (3.74) |
Percentages | ||||
 Parity/age at first birth | ||||
  Nulliparous | 20 | 15 | 22 | 14 |
  Parous, age < 25 years | 31 | 27 | 27 | 28 |
  Parous, age ≥ 25 years | 47 | 56 | 49 | 57 |
 Family history of breast cancer | 5 | 5 | 4 | 9 |
 Benign breast disease | ||||
  Non-proliferative | 4 | 0 | 3 | 1 |
  Proliferative without atypia | 87 | 94 | 87 | 95 |
  Proliferative with atypia | 9 | 6 | 10 | 4 |
 Menopausal status/hormone use | ||||
  Premenopausal | 84 | 93 | 86 | 94 |
  Postmenopausal | 14 | 3 | 11 | 2 |